Abstract This paper presents a hatching algorithm which – while also allows for an implementation in real‐time – is integrated into the production pipeline of computer generated motion picture. Motion picture production pipelines impose special functional and quality requirements. From the functional point of view, the stages of modeling, 3D rendering, and compositing form a pipeline without feed‐back, and frames are rendered independently, possibly on different computers. Thus, no temporal data can be shared between them while flicker free animation needs to be generated. Quality requirements can be grasped as that of dual consistency: the generated hatching must consistently follow object movement and deformation, and, at the same time, it should have a consistent pattern and density in image‐space to provide the hand‐crafted look. In order to meet both requirements, we apply a particle based method and develop an image‐space density control mechanism using rejection sampling and low‐discrepancy sequences. We also discuss the decomposition of rendering tasks according to the main stages of the production pipeline and demonstrate how the artist can define the illustration style in a convenient way.

This paper presents a fast parallel method to solve the radiative transport equation in inhomogeneous participating media. We apply a novel approximation scheme to find a good initial guess for both the direct and scattered components. Then, the initial approximation is used to bootstrap an iterative multiple scattering solver, i.e., we let the iteration concentrate just on the residual problem. This kind of bootstrapping makes the volumetric source approximation more uniform, thus it helps to reduce the discretization artifacts and improves the efficiency of the parallel implementation. The iterative refinement is executed on a face-centered cubic grid. The implementation is based on CUDA and runs on the GPU. For large volumes that do not fit into the GPU memory, we also consider the implementation on a GPU cluster, where the volume is decomposed to blocks according to the available GPU nodes. We show how the communication bottleneck can be avoided in the cluster implementation by not exchanging the boundary conditions in every iteration step. In addition to light photons, we also discuss the generalization of the method to γ-photons that are relevant in medical simulation.

Abstract This survey reviews algorithms that can render specular, i.e. mirror reflections, refractions, and caustics on the GPU. We establish a taxonomy of methods based on the three main different ways of representing the scene and computing ray intersections with the aid of the GPU, including ray tracing in the original geometry, ray tracing in the sampled geometry, and geometry transformation. Having discussed the possibilities of implementing ray tracing, we consider the generation of single reflections/refractions, interobject multiple reflections/refractions, and the general case which also includes self‐reflections or refractions. Moving the focus from the eye to the light sources, caustic effect generation approaches are also examined.

Abstract This paper reviews the latest developments of displacement mapping algorithms implemented on the vertex, geometry, and fragment shaders of graphics cards. Displacement mapping algorithms are classified as per‐vertex and per‐pixel methods. Per‐pixel approaches are further categorized as safe algorithms that aim at correct solutions in all cases, to unsafe techniques that may fail in extreme cases but are usually much faster than safe algorithms, and to combined methods that exploit the robustness of safe and the speed of unsafe techniques. We discuss the possible roles of vertex, geometry and fragment shaders to implement these algorithms. Then the particular GPU‐based bump, parallax, relief, sphere, horizon mapping, cone stepping, local ray tracing, pyramidal and view‐dependent displacement mapping methods, as well as their numerous variations are reviewed providing also implementation details of the shader programs. We present these methods using uniform notations and also point out when different authors called similar concepts differently. In addition to basic displacement mapping, self‐shadowing and silhouette processing are also reviewed. Based on our experiences gained having reimplemented these methods, their performance and quality are compared, and the advantages and disadvantages are fairly presented.